The present invention relates to novel cationic imidazole azo dyes, to processes for their preparation and to their use for dyeing textile materials, leather, paper or glass fibres.
The novel imidazole azo dyes correspond to formula 
wherein
R1, R1xe2x80x2, R2 and R2xe2x80x2 are each independently of the others hydrogen, C1-C4alkyl, halogen or nitro,
R3, R3xe2x80x2, R4 and R4xe2x80x2 are each independently of the others C1-C4alkyl unsubstituted or substituted by OH, C1-C4alkoxy, halogen, CN or phenyl,
R5 is hydrogen or C1-C4alkyl,
R6 is unsubstituted or amino-substituted C5-C12alkyl;
or unsubstituted or amino-substituted C5-C8cycloalkyl;
or phenyl-substituted C1-C4alkyl;
or wherein R5 and R6 together with the nitrogen atom linking them form a piperazine ring, which is substituted, at the nitrogen atom that is not bonded to the phenyl group, by C1-C4-alkyl or phenyl, the alkyl and phenyl radicals mentioned as substituents of the nitrogen atom of the piperazine ring being unsubstituted or substituted by amino,
X1, X2, X3 and X4 are each independently of the others hydrogen, C1-C4alkyl, C1-C4alkoxy or halogen,
Y1 is a bridging member of formula 
or xe2x80x94NHxe2x80x94(CH2)6xe2x80x94NHxe2x80x94, and
Xxe2x88x92 is an anion.
The alkylene groups in the bridging member Y1 may be straight-chain, branched or cyclic and may also be substituted, for example by halogen, alkoxy or hydroxy. In addition, they may be interrupted by hetero atoms, e.g. O or NR5, wherein R5 is hydrogen or C1-C4alkyl. Preference is given to a straight-chain or branched C1-C12alkylene radical. Special preference is given to C1-C6alkylene radicals, more especially C2-C4alkylene radicals. Propylene radicals, especially the 1,3-propylene radical, are of particular importance.
Suitable alkylene radicals are e.g. ethylene, 1,3-propylene, 1,2-propylene, 1,2-butylene, 1,4-butylene, 1,6-hexylene, 1,8-octylene, 1,12-dodecylene, 1,4-cyclohexylene, 2-hydroxy-1,3-propylene, 2-chloro-1,3-propylene and 3-oxa-1,5-pentylene.
According to the invention, alkyl radicals are to be understood as being generally straight-chain or branched alkyl radicals, e.g. methyl, ethyl, n- and iso-propyl and n-, sec- or tert-butyl.
Such alkyl radicals may, like the cycloalkyl groups, be mono- or poly-substituted, for example by hydroxy, carboxy, halogen, cyano, amino or C1-C4alkoxy.
The alkoxy radicals may have e.g. from 1 to 4 carbon atoms, for example methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy and tert-butoxy. The alkoxy groups also may be substituted, e.g. by the radicals listed as possible substituents for alkyl groups, especially by hydroxy or C1-C4alkoxy.
Suitable anions Xxe2x88x92 include both inorganic and organic anions, for example halide, such as chloride, bromide or iodide, sulfate, hydrogen sulfate, methyl sulfate, boron tetrafluoride, aminosulfonate, perchlorate, carbonate, bicarbonate, phosphate, nitrate, benzenesulfonate, formate, acetate, propionate, lactate or complex anions, such as the anion of a zinc chloride double salt.
The anion is generally predetermined by the preparation process. Preferably, chlorides, hydrogen sulfates, sulfates, methosulfates, phosphates, formates, lactates or acetates are present. Highly preferred are chlorides.
Halogen is to be understood as being fluorine, bromine, iodine and especially chlorine.
R1, R1xe2x80x2, R2 and R2xe2x80x2 are preferably each methyl and especially each hydrogen.
R3, R3xe2x80x2, R4 and R4xe2x80x2 are preferably each ethyl, hydroxyethyl or especially methyl.
X1, X2, X3 and X4 are preferably each methoxy, methyl, chlorine or especially hydrogen.
Y1 is preferably a bridging member of formula xe2x80x94NHxe2x80x94(CH2)6xe2x80x94NHxe2x80x94.
R5 is preferably hydrogen, methyl or ethyl, especially hydrogen or methyl. Preferably, R5 is hydrogen.
C5-C12Alkyl radicals R6 are preferably corresponding unsubstituted or amino-substituted
C5-C8alkyl radicals and preferably such C6-C8alkyl radicals.
C5-C8Cycloalkyl radicals R6 are preferably corresponding unsubstituted or amino-substituted cyclohexyl radicals.
Phenyl-substituted C1-C4alkyl R6 is preferably benzyl.
R6 is especially preferably unsubstituted or amino-substituted C5-C12alkyl;
or unsubstituted or amino-substituted C5-C8cycloalkyl;
or phenyl-substituted C1-C4alkyl.
More preferably, R6 is unsubstituted or amino-substituted C5-C8alkyl;
or unsubstituted or amino-substituted cyclohexyl;
or phenyl-substituted C1-C4alkyl.
Especially preferred dyes of formula (1) are those of formula 
wherein
X1, X2, X3 and X4 are each independently of the others hydrogen, methyl or methoxy, especially hydrogen,
Y1 is as defined above under formula (1), especially a bridging member of formula xe2x80x94NHxe2x80x94(CH2)6xe2x80x94NHxe2x80x94, and
Xxe2x88x92 is an anion. As to Xxe2x88x92 the preferences given above apply.
Especially preferred dyes of formula (2) are those of formula 
wherein
X1 and X2 are each independently of the others hydrogen, methyl or methoxy, especially hydrogen, and
R5, R6 and Xxe2x88x92 are as defined above under formula (2). As to R5, R6 and Xxe2x88x92 the abo preferences apply.
Preferably, in formula (2a) R5 is hydrogen.
Preferably, in formula (2a) R6 is unsubstituted or amino-substituted C5-C12alkyl;
or unsubstituted or amino-substituted C5-C8cycloalkyl;
or phenyl-substituted C1-C4alkyl.
The dyes of formulae (1) and (2) can be prepared according to methods known per se (see e.g. EP-A-714 954).
The dyes of formula (1) can be obtained, for example, by reacting a compound of formula 
with a diamine of formula 
or
NH2xe2x80x94(CH2)6xe2x80x94NH2xe2x80x83xe2x80x83(4b)
wherein the substituents have the definitions and preferred meanings indicated above. Alternatively, it is also possible to use as compounds of formula (3) those compounds which, instead of the methoxy group indicated, contain halogen, e.g. chlorine, or C2-C4alkoxy. The compounds of formulae (3), (4a) and (4b) are known or can be prepared in a manner known per se. For example, the compounds of formula (3) can be obtained by diazotising 4-alkoxyanilines, coupling the product with an imidazole and then carrying out alkylation and quaternisation.
The reaction of a compound of formula (3) with a diamine of formula (4a) or (4b) can be carried out, for example, at a temperature of about from 40 to 100xc2x0 C., preferably from 40 to 70xc2x0 C., optionally under pressure and/or in an inert gas atmosphere, and in an inert solvent, e.g. in water or aliphatic alcohols, e.g. C1-C8alcohols, such as methanol, ethanol or especially isopropanol, but more especially in aprotic polar solvents, such as dimethylformamide or dimethyl sulfoxide. In the case of diamines that are liquid under the reaction conditions, it is possible, if desired, to dispense with a solvent.
The dyes of formula (2) can be obtained, for example, in a similar way as given above for the preparation of the compounds of formula (1). However, instead of the diamines of formulae (4a) and (4b) an amine of formula HN(R5)R6 is used.
The dyes of formulae (1) and (2) according to the invention are suitable for dyeing polyacrylonitrile materials and leather, but especially for dyeing paper, since they possess a high substantivity for that substrate. The dyes give dyeings in red shades. The resulting dyeings are distinguished by good fastness properties. The effluents are in most cases completely colourless.
The dyes of formula (1) or (2) may also be used in mixtures with other cationic dyes. Especially preferred dye mixtures are those which contain a dye of formula (1) or a dye of formula (2) and a cationic copper phthalocyanine dye. Using such mixtures there are obtained on paper dyeings in highly attractive neutral shades. Suitable copper phthalocyanine dyes are those dyes which are known from the literature and can be used for the dyeing of paper, especially the dyes described in EP-A-0 184 991, DE-A-3 111 199 and EP-A-0 174 586.
The dyes of formula (1) or (2) can be formulated as a solid or liquid commercial form and employed for the dyeing of paper.
In the form of powder or granules, the dyes are used especially in discontinuous mass dyeing, in which the dye is added in batches to the pulper, hollander or mixing vat. In this case the dyes are preferably used in the form of dye preparations which may comprise diluents, e.g. urea as solubiliser, dextrins, Glauber""s salt, sodium chloride and dispersants, dusting agents and sequestrants, such as tetrasodium pyrophosphate.
The invention accordingly relates also to solid dye preparations for the dyeing of paper which comprise dyes of formula (1) or (2).
In recent years, the use of concentrated aqueous solutions of dyes has gained in importance, specifically because of the advantages which such solutions have over dyes in powder form. By using solutions, the difficulties associated with the formation of dust are avoided and the user is freed from the time-consuming and often difficult dissolution of the dye powder in water. The use of concentrated solutions has been prompted furthermore by the development of continuous dyeing processes for paper, since in those processes it is advantageous to add the solution directly to the hollander or at any other suitable point in the paper-making.
The invention therefore relates also to concentrated aqueous solutions of dyes of formula (1) or (2) which comprise, for example, from 1 to 50 percent by weight, especially from 5 to 40 percent by weight, and preferably from 8 to 30 percent by weight, dye, based on the total weight of the solution.
Concentrated aqueous solutions of dyes of formula (1) or (2) can be prepared, for example, by filtering the dye suspension obtained in the preparation of the dye, subjecting the filtrate, if desired, to desalination, for example by a membrane separation technique, and then stabilising it with an acid, for example formic acid, acetic acid or lactic acid, and by the addition of auxiliaries, such as urea, xcex5-caprolactam or polyethylene glycol.
The dye solutions so prepared preferably contain from 400 to 900 parts of water, from 0 to 400 parts of an organic carboxylic acid, for example formic acid, acetic acid, propionic acid or lactic acid, and from 0 to 200 parts of further additives, such as urea, xcex5-caprolactam or polyethylene glycol, per 100 parts of dye.
The aqueous concentrates according to the invention, which are stable at storage temperatures of up to xe2x88x925xc2x0 C., are suitable for the dyeing of paper, on which they produce attractive red shades.
The dyes of formula (1) or (2) can also be employed for the dyeing of textile materials of cellulose, for example cotton, and for the dyeing of leather and glass fibres.
The following Examples serve to illustrate the invention but do not limit the invention thereto. Parts and percentages relate to weight, unless otherwise indicated.